1. Field of Invention
The present invention generally relates to a package structure, and particularly to a package structure of a light-emitting device.
2. Description of Related Art
In comparison with conventional bulbs, the light-emitting diodes (LEDs) are characterized by compactness, long lifetime, low power consumption, free of mercury (non-pollution), and so on. With advancement of luminance efficiency, applications of fluorescent lamps and incandescent bulbs are gradually replaced with LEDs in some areas. For example, the LEDs have been employed to high-speed light sources of scanners, back light sources of liquid crystal displays (LCDs), illumination of the instrument panels, traffic signs and general illumination devices.
Despite the aforesaid advantages, the LEDs are often damaged by abnormal voltages or electrostatic discharge (ESD). Conventionally, the LED and a Zener diode are connected in parallel to prevent the LED from being damaged by the abnormal voltage or ESD.
FIG. 1A is a top view depicting a conventional LED package structure, while FIG. 1B is a cross-sectional view of the LED package structure of FIG. 1A. Referring to FIGS. 14 and 1B, the conventional LED package structure 100 includes a first lead 110, a second lead 120, an encapsulant 130, an LED chip 140, and a Zener diode 150. The first lead 110 is disposed beside the second lead 120, and parts of the first lead 110 and the second lead 120 are packaged by the encapsulant 130. The encapsulant 130 has a cavity 132 SO as to expose parts of the first lead 110 and the second lead 120.
In addition, the LED chip 140 is disposed on the first lead 110 within the cavity 132. A cathode of the LED chip 140 is electrically connected to the first lead 110 through a wire 162 while an anode thereof is electrically connected to the second lead 120 through a wire 164. The Zener diode 150 is disposed on the second lead 120 within the cavity 132. The cathode of the Zener diode 150 is electrically connected to the second lead 120 directly while the anode thereof is electrically connected to the first lead 110 through a wire 166.
According to the prior art, the disposition of the Zener diode 150 prevents the LED chip 140 from being damaged by ESD. However, the Zener diode 150 blocks parts of the light emitted by the LED chip 140, which deteriorates the luminescence efficiency of the LED package structure 100.